A sulfide-based solid electrolyte and a method for preparing sulfide-based solid electrolyte

Abstract

A sulfide-based solid electrolyte having improved ion conductivity and a method for preparing the same are provided. The sulfide-based solid electrolyte contains a Group 2 element and has an argyrodite-type crystal structure. The sulfide-based solid electrolyte is represented by Li 7−x−2y M y PS 6−x Ha x , wherein M represents at least one element selected from Group 2 elements, Ha is at least one element selected from halogen elements and includes Br, and x and y satisfy 0<x<2.5 and 0<y<0.45, and wherein the sulfide-based solid electrolyte has a lattice volume of from 950 to 980 Å 3 .

1 . A sulfide-based solid electrolyte containing a Group 2 element and having an argyrodite-type crystal structure,
 wherein the sulfide-based solid electrolyte is represented by Li 7−x−2y M y PS 6−x Ha x , wherein M represents at least one element selected from Group 2 elements, Ha is at least one element selected from halogen elements and includes Br, and x and y satisfy 0<x<2.5 and 0<y<0.45, and   wherein the sulfide-based solid electrolyte has a lattice volume of from 950 to 980 Å 3 .   
     
     
         2 . The sulfide-based solid electrolyte according to  claim 1 , wherein y satisfies 0<y<0.1. 
     
     
         3 . The sulfide-based solid electrolyte according to  claim 1 , wherein M is at least one selected from the group consisting of Mg, Ca, Sr and Ba. 
     
     
         4 . The sulfide-based solid electrolyte according to  claim 1 , wherein M is Ca. 
     
     
         5 . The sulfide-based solid electrolyte according to  claim 1 , wherein the sulfide-based solid electrolyte has an ion conductivity of 2 mS/cm or more. 
     
     
         6 . The sulfide-based solid electrolyte according to  claim 1 , wherein the sulfide-based solid electrolyte does not comprise any impurity phase other than argyrodite phase. 
     
     
         7 . The sulfide-based solid electrolyte according to  claim 1 , wherein the sulfide-based solid electrolyte has a lattice volume of from 958 to 966 Å 3 . 
     
     
         8 . A method for preparing the sulfide-based solid electrolyte as defined in  claim 1 , the method comprising:
 mixing a lithium source, a Group 2 element source, a phosphorus source, a sulfur source and a halogen source to obtain a mixture; and   
       firing the mixture under inert atmosphere at a temperature of from 250 to 600° C.